1. Field of the Invention
The present invention relates to a heat exchanger. The heat exchanger of the present invention is effectively used when it is applied to a radiator of a water-cooled internal combustion engine in which heat is exchanged between cooling water and air.
2. Description of the Related Art
A conventional radiator includes: a plurality of tubes in which cooling water flows and header tanks, which are arranged on both end sides of the tubes in the longitudinal direction of the tubes and extend in a direction substantially perpendicular to the longitudinal direction of the tubes, communicated with the plurality of tubes. Each header tank includes a core plate into which the tubes are inserted and fixed and a tank portion which, together with the core plate, composes a space in the header tank.
Conventionally, embossed portions, which are respectively formed into a recessed shape or a protruded shape, are provided between holes formed on the core plate into which the tubes are inserted, so that the mechanical strength of the core plate can be enhanced, that is, the deformation strength of the core plate against bending and twisting can be enhanced. This constitution is disclosed, for example, in the official gazette of Japanese Unexamined Patent Publication No. 12-283689.
In this connection, in the radiator described in the official gazette of Japanese Unexamined Patent Publication No. 12-283689, when a pitch between the tubes is decreased so as to reduce the size of the radiator, it becomes impossible to provide embossed portions between the holes into which the tubes are inserted. Alternatively, the size of the embossed portions must be reduced. Accordingly, it is impossible to ensure a sufficiently high mechanical strength.